PTL 1 discloses a projection device in which a projection optical system including a reflection surface is used. The projection device is a projection optical system that magnifies and projects an image formed in a light valve onto a projection surface, and the projection device includes a plurality of lenses. The projection device includes a positive-power lens optical system that forms an intermediate image of the image, a positive-power first reflection surface that reflects a light flux diverging after the formation of the intermediate image and forms the image on the projection surface, and a second reflection surface that causes the light output from the lens optical system to strike on the first reflection surface between the projection surface and the light valve. Therefore, a large screen in which chromatic aberration and distortion are reduced can be projected.
However, in the projection device of PTL 1, a distance between the first reflection surface and the second reflection surface is lengthened, which results in enlargement (high profile) of the projection device.